Tuesday, January 16, 2018

Overnight we experienced a rare weather event in northeast Louisiana: it snowed! Not only did it snow, but it didn't immediately melt. Today, the temperature didn't reach 30 degrees, so the snow remains.

Magnolia grandiflora leaves

the mayhaws

Looking eastward: the two trees on the south side of the bridge are leaning toward the south, and the wintry mix, blowing in from the north, accumulated on the leaning trunks.

Prunus mexicana

Juniperus virginiana in the Mickle Hall parking lot

Tree of the Week: Evergreen Sweetbay Magnolia (Magnolia virginiana var. australis)

Yesterday in Caddo parish we had sunny, 60-degree-weather. It was a pleasurable day for taking pictures of our tree of the week, the evergreen sweetbay magnolia (Magnolia virginiana var. australis). This tree is very much like any other sweetbay, but it keeps more of its leaves during the winter months. So, in the middle of January, the dark green leaves remain on the tree.

There are two evergreen sweetbays in the arboretum collection. Ed Leuck acquired these two trees from John Mayronne at a meeting of the Louisiana Native Plant Society. The meeting was held January 26, 1997, and the trees were planted the following November, making them over 20 years old. The photos below show that one of the two trees is significantly shorter than the other. The shorter tree is growing on the north side of its companion, meaning that it gets less sun. This could explain some of the difference. But another explanation is that the shorter tree was crushed by a falling Pinus taeda on April Fool's Day in 2000. Both trees are in good condition today!

After such a beautiful day, the weather quickly changed. The rain started in the evening and transitioned from sleet to snow by midnight. Waking up this morning, we had a Louisiana-style winter wonderland. The rare event necessitated a photography expedition. So, we have a few pictures of the evergreen sweetbays in the snow.

The grass isn't green anymore, and the old oak trees are looming overhead without any leaves on their branches. Meanwhile, this variety of sweetbay magnolia remains green, as if it's still summer.
There is a narrow drainage channel, or "creek", that runs west to east through the arboretum. One sweetbay was planted on the north side of the creek, the other on the south side. Although the two trees are the same age, one tree is clearly shorter than the other, suggesting a competition for resources. In this photo, we are looking eastward.
The tree on the north side of the creek has a single trunk, while the other tree has a multi-trunk form.
The multi-trunk form is common for sweetbays. Surface roots aren't a problem with these two trees.
The elliptic leaves are dark green in the middle of January.
Sweetbay leaves are white underneath. On a sunny, windy day the leaves have a silvery appearance, making the tree identifiable from a distance. 
After a beautiful, sunny, 60-degree day, the weather rapidly turned cold. Approximately 2 inches of snow fell during the night. 
The weather was cold enough to allow the snow to accumulate.
Snow remained on the evergreen leaves during the following day.

For more information about this species consult the following:
LSU AgCenter
United States Department of Agriculture
Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)
University of Florida IFAS Extension
NC State Extension

Thursday, January 11, 2018

Tree of the Week: the Mayhaws (Crataegus opaca and Crataegus aestivalis)

Over the past couple of weeks we have been studying the eastern red cedar (Juniperus virginiana). This attention has resulted in a decision to deal with the irksome cedar-apple-rust, whose galls are currently developing in the eastern red cedars. These galls are expected to 'open' soon, releasing their spores into the environment. Rather than targeting the galls themselves, which are housed in the inaccessible heights of the cedars, we decided to begin with a more manageable project: protecting the alternative hosts, and victims, of the rust.

The eastern and western mayhaws are susceptible to infection. These are small, early-blooming fruit trees that produce cranberry-like fruits. They are a southern gem. The best known way to protect the fruit tree is to spray the flower buds just before they open. Because the buds are currently developing, now is the time for action.

There are four mayhaws in the arboretum collection. Three western mayhaws (Crataegus opaca) are from Louisiana Forestry. They were acquired in 1994, and planted the following November, making them more than 20 years old. Our only eastern mayhaw (Crataegus aestivalis) was purchased from Woodlanders Nursery (Aiken, South Carolina) and planted along with the others. The four mayhaws dwell south of the long white wooden bridge, near the drainage channel that runs through the arboretum. The pictures below show that there has been some competition for sunlight; the crowns of the four trees have grown together.

The pictures below were taken on a cool cloudy January day.

We are looking toward the east, with the red bricks of Mickle Hall in the background. The eastern mayhaw is pictured center. Two western mayhaws are pictured to the left of the center tree, and one western mayhaw is pictured to the right. All three western mayhaws are leaning south, and one trunk is noticeably thicker than the other three.
Here we are looking north. The one mayhaw trunk is still noticeably thicker than the other three.
Two flowers were spotted on the branches, blooming ahead of season. This pretty white flower was found on the southern-most western mayhaw (C. opaca). As you can see, the flower appears in a cluster.
Most of the flower buds look like this. They aren't opening yet.
The buds are a rosy pink.
After researching cedar-apple-rust and comparing several options for treatment, Immunox was found to be the best option for protecting the mayhaws.
There are specific instructions for mayhaws on the the Immunox bottle. For our sprayer, we mixed 2/3 fluid ounce of Immunox for each gallon. The instructions tell us that the best time to spray is when the buds are opening. Other recommendations advise a first spray during the "pink bud stage," which is the option we chose.
Precautions were taken to protect our skin from the fungicide solution, wearing rubber gloves, hats, and protective eye-wear.
The instructions state "apply to all parts of the tree to point of runoff", so we made sure to thoroughly spray the mayhaw branches.
This is the gray bark of the eastern mayhaw (C. aestivalis). Note the orange specks of new bark (see C. marshallii). The tree trunks were also thoroughly sprayed with the fungicide solution. 

You can see more photos of the arboretum's eastern mayhaw here
And you can find photos of the western mayhaw here

For more information about the mayhaws, consult the following links:
United States Department of Agriculture -- Western Mayhaw (Crataegus opaca)
United States Department of Agriculture -- Eastern Mayhaw (Crataegus aestivalis)
University of Florida IFAS Extension -- Eastern Mayhaw (C. aestivalis)
Temperate Climate Permaculture

Friday, January 5, 2018

Tree of the Week: Eastern Red Cedar (Juniperus virginiana) VOLUME II

2018 arrived in Caddo parish with an arctic chill. This past week we experienced temperatures in the teens, finally putting the mosquitoes to bed for the winter (*fingers crossed*). Thankfully the cold air wasn't accompanied by any precipitation, so the trees and woody vines were unfazed.

With most of the trees leaf-less, the evergreen species stand out. This week we are taking another look at the eastern red cedar (Juniperus virginiana). Last week we discussed two volunteers growing on the slope west of Hamilton Hall. The individual pictured below is also a volunteer, approximately 15 years of age. It germinated under the canopy of an old sweet gum tree (Liquidambar styraciflua). The sweet gum was removed more than a decade ago, allowing the eastern red cedar plenty of room to stretch its limbs.
Our tree of the week is pictured center. A few other evergreen species are also pictured. At the far left, we have the leaves of Magnolia grandiflora. Towering over the landscape, behind the eastern red cedar, is a very old loblolly pine (Pinus taeda). Palmettos, the fetter-bush, and a red bay are the other spots of green.
This eastern red cedar has the characteristic Christmas-tree appearance. It germinated on the south side of a very large sweet gum tree, and had the sweet gum lived, the eastern red cedar would not have had the necessary room to develop its conical shape.
The pale blue cones indicate that this is a female eastern red cedar.
Zooming in on the female cones, we also see the scale-like leaves.

Among the leaves and cones, something else is hanging from the branches.
This irregularly shaped brown growth might be mistaken for tree reproduction. It's actually a gall produced by a fungus called Gymnosporangium juniperi-virginianae. This fungus is responsible for the plant disease 'cedar-apple rust'.
The eastern red cedar serves as a host for the fungus, which is detrimental to susceptible apple trees, hence the name 'cedar apple rust'. Pictured above: the gall was removed from the tree and broken into pieces revealing a hard greenish-white interior. If we had allowed it to continue its life-cycle, it would have continued to develop until the first several warm rainy days, at which time it would release spores into the environment.
This is a dead gall. It appears to have killed the twig.

Despite the fungal infection, this eastern red cedar is doing marvelously. Overall, eastern red cedars are not harmed by the cedar apple rust.
Typical reddish-brown shreddy bark of the eastern red cedar